Hey guys need help ASAP!! who knows the definition of the Mormon trail??

The Mormon pioneer run began in 1846, when Young and his followers were driven from Nauvoo. After leaving, they aimed to establish a new home for the church in the Great Basin and crossed Iowa. Along their way, some were assigned to establish settlements and to plant and harvest crops for later emigrants.

Explanation:

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."